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[DebugInfo][NewGVN] Fix debug value loss #147634

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Merged
merged 4 commits into from
Jul 21, 2025
Merged

[DebugInfo][NewGVN] Fix debug value loss #147634

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95cb833
fix #147511
Apochens Jul 9, 2025
4dc155a
replacing dbg uses instead of salvaging
Apochens Jul 13, 2025
f657571
refine the test comment
Apochens Jul 13, 2025
9162ff7
format
Apochens Jul 13, 2025
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10 changes: 10 additions & 0 deletions llvm/lib/Transforms/Scalar/NewGVN.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,7 @@
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
Expand Down Expand Up @@ -4076,6 +4077,15 @@ bool NewGVN::eliminateInstructions(Function &F) {
if (!match(DefI, m_Intrinsic<Intrinsic::ssa_copy>()))
patchReplacementInstruction(DefI, DominatingLeader);

SmallVector<DbgVariableIntrinsic *> DbgUsers;
SmallVector<DbgVariableRecord *> DVRUsers;
findDbgUsers(DbgUsers, DefI, &DVRUsers);

for (auto *DVI : DbgUsers)
DVI->replaceVariableLocationOp(DefI, DominatingLeader);
for (auto *DVR : DVRUsers)
DVR->replaceVariableLocationOp(DefI, DominatingLeader);

markInstructionForDeletion(DefI);
}
}
Expand Down
45 changes: 45 additions & 0 deletions llvm/test/Transforms/NewGVN/salvage-eliminate-instruction.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
; RUN: opt -S -passes=newgvn %s | FileCheck %s

; Check that eliminateInstruction() replaces the debug uses of the instructions
; marked for deletion with the dominating leader.

define void @binop(i32 %x, i32 %y) !dbg !5 {
; CHECK: #dbg_value(i32 %add1, [[META9:![0-9]+]], !DIExpression(), [[META12:![0-9]+]])
; CHECK-NEXT: #dbg_value(i32 %add1, [[META11:![0-9]+]], !DIExpression(), [[META13:![0-9]+]])
;
%add1 = add i32 %x, %y, !dbg !12
#dbg_value(i32 %add1, !9, !DIExpression(), !12)
%add2 = add i32 %y, %x, !dbg !13
#dbg_value(i32 %add2, !11, !DIExpression(), !13)
call void @use(i32 %add1, i32 %add2), !dbg !14
ret void, !dbg !15
}

declare void @use(i32, i32)

!llvm.dbg.cu = !{!0}
!llvm.debugify = !{!2, !3}
!llvm.module.flags = !{!4}

!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
!1 = !DIFile(filename: "/app/example.ll", directory: "/")
!2 = !{i32 4}
!3 = !{i32 2}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = distinct !DISubprogram(name: "binop", linkageName: "binop", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
!6 = !DISubroutineType(types: !7)
!7 = !{}
!8 = !{!9, !11}
!9 = !DILocalVariable(name: "1", scope: !5, file: !1, line: 1, type: !10)
!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
!11 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 2, type: !10)
!12 = !DILocation(line: 1, column: 1, scope: !5)
!13 = !DILocation(line: 2, column: 1, scope: !5)
!14 = !DILocation(line: 3, column: 1, scope: !5)
!15 = !DILocation(line: 4, column: 1, scope: !5)
;.
; CHECK: [[META9]] = !DILocalVariable(name: "1",
; CHECK: [[META11]] = !DILocalVariable(name: "2",
; CHECK: [[META12]] = !DILocation(line: 1,
; CHECK: [[META13]] = !DILocation(line: 2,
;.
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